This invention relates to means for connecting the ends of a pair of sheet metal duct sections. The invention particularly involves an assembly of the type including frame members defining flanges located at a duct end with adjacent frame members joined to each other by angular corner pieces.
The prior art, particularly Mez U.S. Pat. No. 3,712,650 and Arnoldt U.S. Pat. No. 4,218,079 disclose flange connections for connecting the ends of rectangular air conditioning ducts. These arrangements include flange portions having a horizontal leg portion secured to the end portion of the duct and a vertical channel-shaped leg for receiving the arms of an angular corner piece.
In the Mez patent, the angular corner pieces have arm portions that extend into an opening in the vertical leg. The arm portions are so dimensioned vertically that the lower surface of the arms abut the lower wall of the horizontal flange. With this arrangement, the end of the duct wall abuts or rests against a surface of the corner piece arm extending into the channel-shaped opening.
The Arnoldt patent also provides flange portions having an upstanding channel-shaped leg portion with a front wall and a rear wall forming a longitudinal opening therebetween, and a duct receiving leg portion with a top wall and a bottom wall. A corner piece is insertable in the longitudinal opening, and provision is also made for gasket means positioned in the longitudinal opening adjacent the duct receiving leg bottom wall. The gasket means is adapted to be positioned between the duct end portion and the upper surface of the duct receiving leg bottom wall to sealingly connect the duct end portion to the frame flange portion.
In the Mez and Arnoldt arrangements, bolts or the like are utilized for attaching the corner pieces at one duct end with corner pieces of an adjacent duct end. A suitable clip may then be snapped in place at the extremities of the adjoining frames at the respective duct ends. The assemblies thus obtained are of satisfactory strength; however, multiple assembly steps requiring skill and experience are involved in achieving this assembly.
Siegwart U.S. Pat. No. 3,443,601 discloses another arrangement for joining duct ends. In accordance with this teaching, frame-like portions are formed as integral parts of a duct end, and clips or ledges are provided for engagement with adjacent frame-like portions. The frame-like portions and/or the clips are designed so that a resilient connection is achieved with a view toward insuring a satisfactory attachment. Although this arrangement involves fewer assembly steps, the assembly operation is difficult, and the arrangement is not completely satisfactory from a strength standpoint.